Addition of Hydroxyurea to Fludarabine, Cytarabine, Idarubicin and Venetoclax Salvage Therapy for Adults With Relapsed or Refractory Acute Myeloid Leukemia (FLAsH-IV-AML)

FLAsH-IV-AML: A Phase I/II Multi-center Study to Assess the Tolerability and Efficacy of the Addition of Hydroxyurea to Salvage Treatment With Fludarabine, Ara-C, Idarubicin and Venetoclax for Adults With Relapsed or Refractory Acute Myeloid Leukemia

This study is evaluating a new treatment approach for adults with acute myeloid leukemia (AML) that has either returned after previous treatment or has not responded to treatment. Outcomes for these patients are often poor, and there is a need for more effective therapies.

The study is investigating whether adding hydroxyurea to a combination of established AML medicines (fludarabine, cytarabine, idarubicin, and venetoclax) is safe and tolerable and can improve treatment results. Laboratory studies suggest that hydroxyurea may help leukemia cells become more sensitive to treatment and may increase the effectiveness of chemotherapy.

The study is being conducted in two parts. In the first part, researchers will determine the safest and most appropriate dose of hydroxyurea when given together with the study treatment. In the second part, researchers will evaluate whether adding hydroxyurea improves treatment outcomes, including the length of time patients remain free from disease progression, relapse, or death.

The overall goal of the study is to determine whether adding hydroxyurea to standard treatment for relapsed or refractory AML is safe and may improve patient outcomes.

Study Overview

• Status: Not yet recruiting
• Conditions: R/R AML
• Intervention / Treatment: Drug: Hydroxycarbamid

• Study Type: Interventional
• Enrollment (Estimated): 26
• Phase: Phase 2; Phase 1

Contacts and Locations

• Study Contact: Name: Christer C Nilsson, Md PhD; Phone Number: 08-123 800 00; Email: christer.c.nilsson@regionstockholm.se

Study Locations

• Sweden
  • Stockholm, Sweden
    • Medical Unit Hematology, Karolinska University Hospital
    • Contact: Merja Jansson; Phone Number: +46 8 123 827 08; Email: merja.jansson@regionstockholm.se
    • Principal Investigator: Christer C Nilsson, MD PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. A diagnosis of either:

   • Refractory AML defined as having > 10% bone marrow blasts after induction with one cycle of intensive chemotherapy or no CR after two cycles of chemotherapy.
   • Relapsed disease (including extramedullary disease) according to the 2022 ELN criteria (see appendix A).
   • MRD relapse defined as evidence of measurable (minimal) residual disease (MRD) at a level of ≥5%, as determined by either molecular assays or multiparameter flow cytometry.
2. Age 18 years or older.
3. ECOG Performance Status ≤ 2.

4. Adequate renal and hepatic functions as indicated by the following laboratory values:

   • Creatinine clearance ≥ 30 mL/min calculated by the Cockcroft Gault formula.
   • Serum bilirubin ≤ 3 x upper limit of normal (ULN), unless due to Gilbert's syndrome.
   • Alanine aminotransferase (ALAT) ≤ 5 x ULN.
5. Considered fit for intensive chemotherapy.
6. Male patients must use a latex condom during any sexual contact with women of childbearing potential, even if they have undergone a successful vasectomy and must agree to avoid fathering a child (while on therapy and for 6 months after the final study drug administration). In addition, their female partners of childbearing potential must use a highly effective method of birth control.
7. Male patient must not donate sperm starting at screening and throughout the study period and for 6 months after the final study drug administration.
8. Female patients of nonchildbearing potential must be postmenopausal (defined as at least 1 year without any menses), documented surgically sterile prior to screening.
9. Female patients of childbearing potential must agree to avoid pregnancy during the study and for 6 months after the final study drug administration and have a negative urine or serum pregnancy test at screening, and if heterosexually active, agree to consistently apply one highly effective method of birth control in combination to a barrier method for the duration of the study and for 6 months after the final study drug administration.
10. The subject has given their written consent to participate in the trial.
11. Patient is capable of giving informed consent.

Exclusion Criteria:

1. Acute promyelocytic leukemia.
2. WBC ≥30; pretreatment with HU to reduce the level of WBC <30 is allowed in part B/phase II of the trial.
3. TP53 double hit mutation / biallelic TP53 inactivation.
4. CNS leukemia.
5. Relapse within 3 months from the date of allo-HCT.
6. Uncontrolled infection.
7. ECOG Performance Status > 2.
8. Major organ failure precluding administration of planned chemotherapy

9. Cardiac dysfunction as defined by:

   • Myocardial infarction within the last 3 months of study entry, or
   • Reduced left ventricular function with an ejection fraction < 50% as measured by echocardiogram (will only be performed when clinically suspected) or
   • Unstable angina or
   • New York Heart Association (NYHA) grade III or IV congestive heart failure (see appendix C) or
   • Severe cardiac arrhythmias
10. Age 75 years or older.
11. Known intolerance to any of the chemotherapeutic drugs in the protocol.
12. Positive pregnancy test.
13. Lactating female or female of childbearing potential not using adequate contraception.
14. Known inherited bone marrow failure syndromes (e.g., Fanconi anemia, Dyskeratosis congenita and related telomeropathies (e.g., TERT, TERC, DKC1 mutations).
15. Patients with a history of non-compliance to medical regimens or who are considered unreliable with respect to compliance.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Hydroxyurea added to fludarabine, ara-C, idarubicin and venetoclax	Drug: Hydroxycarbamid; Hydroxyurea 500-1000 mg administered 1 hour before each infusion of cytarabine.; Other Names: Hydroxyurea

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
1-year EFS	Defined as event-free-survial from the time from initiation of study treatment to the first occurrence of treatment failure, hematologic relapse from CR/CRi, or death from any cause.	From initiation of study treatment to the first occurrence of treatment failure, hematologic relapse after CR/CRi, or death from any cause, whichever occurs first, assessed up to 365 days.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Safety and tolerability: incidence and severity of treatment-emergent adverse events	Frequency, nature and severity of non-hematological toxicities, including potential ara-C or fludarabine related neurological or dermatological adverse events.	From registration in the study until 60 days after the last dose of treatment.
Overall survival (OS)	Overall survival (OS), defined as the time from initiation of study treatment to death from any cause, with survival estimates reported at 1 and 2 years after initiation of study treatment.	From initiation of study treatment through 2 years of follow-up.
2-year event-free survival (EFS)	Time from initiation of study treatment to the first occurrence of treatment failure, hematologic relapse after CR/CRi, or death from any cause, whichever occurs first.	From initiation of study treatment through 2 years of follow-up.
Relapse-free survival (RFS)	Overall survival (OS), defined as the time from initiation of study treatment to the date of death from any cause or hematologic relapse from CR/CRi, with survival estimates reported at 1 and 2 years after initiation of study treatment.	From initiation of study treatment through 2 years of follow-up.
Cumulative incidence of hematologic relapse	Cumulative incidence of hematologic relapse after achievement of CR/CRi, reported at 1 and 2 years. Death without prior relapse will be treated as a competing risk.	From initiation of study treatment through 2 years of follow-up.
Response rate	Proportion of patients achieving complete remission (CR), complete remission with incomplete hematologic recovery (CRi), morphologic leukemia-free state (MLFS), partial remission (PR) and minimal residual disease (MRD) negativity.	At response assessment after Cycle 1 (between Day 25 and Day 35 from the start of Cycle 1).
Time to hematopoietic recovery	Time to hematopoietic recovery (ANC 0.5 and 1.0 x 109/L; platelets 50 and 100 x 109/L) after each chemotherapy treatment cycle, defined as the time from the start of the cycle until recovery.	From the start of each treatment cycle until hematopoietic recovery. Treatment cycles are of variable duration, with no predefined cycle length; the subsequent cycle is initiated only after hematopoietic recovery.
Rate of patients bridged to allo-HCT	Proportion of patients undergoing allogeneic hematopoietic cell transplantation.	From treatment initiation until allogeneic hematopoietic cell transplantation, relapse/progression, death, or 2 years of follow-up, whichever occurs first.
Early mortality (30-day and 60-day mortality)	Proportion of patients who die from any cause within 30 and 60 days after initiation of study treatment.	30 and 60 days after initiation of study treatment.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intracellular accumulation of ara-CTP and F-ara-ATP	Assessment of intracellular accumulation of ara-CTP and F-ara-ATP in circulating blasts as a biomarker for efficacy of added hydroxyurea.	During the first 2 days of treatment (run-in phase), at 4 predefined time points.
SAMHD1 protein expression	Assessment of SAMHD1 protein expression in blasts before treatment as a biomarker for efficacy of added hydroxyurea	At baseline, prior to initiation of study treatment.

Collaborators and Investigators

• Sponsor: Christer C Nilsson
• Collaborators: Karolinska University Hospital
• Investigators: Principal Investigator: Christer C Nilsson, MD PhD, Karolinska University Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): October 1, 2026
• Primary Completion (Estimated): June 1, 2029
• Study Completion (Estimated): September 1, 2034

Study Registration Dates

• First Submitted: June 12, 2026
• First Submitted That Met QC Criteria: August 11, 2026
• First Posted (Actual): August 17, 2026

Study Record Updates

• Last Update Posted (Actual): August 17, 2026
• Last Update Submitted That Met QC Criteria: August 11, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Hydroxyurea; Venetoclax; FLAG-Ida
• Additional Relevant MeSH Terms: Organic Chemicals; Amides; Urea; Hydroxyurea
• Other Study ID Numbers: FLAsH-IV-AML

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

IPD Plan Description

IPD Sharing Statement: Individual participant data (IPD) will not be shared.

Justification: The study is an early-phase investigator-initiated clinical trial in a rare and high-risk patient population. Due to the small sample size, detailed molecular data, and potential risk of re-identification despite de-identification, individual participant data will not be made publicly available.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No